Temporal validity - pointless new syntax or something quite useful?

I saw Julian Dyke briefly dicusss this topic at the UKOUG this year and I immediately thought this might give us a performance benefit as we have a lot of time based data with start and end dates.

My first thought was this - if this new 'column' that is being added would somehow be stored in some special format that would allow indexing of it to rapidly find the answers to queries where previously we would have to range scans on the data for > and < for the start and end date of data.

So here the new bit is the 'is_active' column which defines the start_date column and the end_date column as the beginning and end of when the data is active - in the case above if we have a start date of 1/1/2010 and an end date of 1/1/2011 then the whole year in between those dates the data is active.